Electrically heated cushion



H. KINDERMANN ET AL ELECTRIC'AIJLY HEATED CUSHION F iled March 29, 1934 Aug. 27, 1935.

I I nventorsz 1 H/Ermdun l- 07V"? m'rm BY: mm.

Patented Aug. 27, 1935 UNITED STATES PATENT OFFICE v 2.01mi ELECTRICALLY nearer) cosmos Harms Kindermann and Grete Kindermann, nee Huesmann, Radlita, Post Steinan, Germany PIIlication March 29,

In Germany 1934, Serial No. 718,083

April 1, 1933 3 Claim. (Cl. 219-48) This invention relates to improvements in electrically heated cushions of the usual type consisting of heating wircs, a fabric to which the heating wires are secured (heating wire carrier) and one or more protecting covers. The object of the invention is to make the cushion flreproof in all operating conditions.

It is already known to cover the heating wires or spirals with thick or thin single or multiple asbestos threads. This covering is not suflicient to prevent short circuit and burning of the cushion as, for example, when the heating wire is broken and the wire ends come into contact through the asbestos covering. The heating wire carrier consistingjof fabric similar to a dish-cloth on which or' in which the asbestos covered wires are inserted is ignited by the sparks or by the heating of the wires and then smoulders like tinder.

proof by impregnation by suitable means. The impregnation of a fabric for the present purpose can be effected byvarious means such as waterglass molasses with calcium or ammonium borate and a small addition of acid, sodium molybdate or the like. Experience has, however, shown that while the known impregnatingv means prevent burning with flames, smouldering of the fabric may still take place under certain circumstances This is of especial importance in a heated cushion because the fabric forming the heating wire carrier in a heated cushion is surrounded by further protective coverings usually a bag of flannel and a further bag of linen. when the heater wire carrier smoulders it is possible for the surrounding fabric to become ignited andto burn.

Some of the known means have thefurtherdisadvantagctha tatthecomparativeiy high temperatures ofv 80 C. and more. which occur in such a heated cushion, the action 45 of the heat on the impregnating means causes the production of imheaithy vapours and after a time'the impregnating agent evaporates or an unpleasant smell is produced which is found very detrimentalin the use'of the cushion These disadvantages are avoided according to the invention by the fabric acting as heating wire carrier being impregnated with a mecial solution which consists essentially of ammonium sulphate, ammonium chloride, boric acid and boraxdissolvedinwater,towhichispreferably This danger of fire in the known heated cushions is effectively prevented by the present in-' vention by the fabric carrying the heater wires, which itself is inflammable, being made flreadded small quantities of a condensation product of urea and formaldehyde, for example. the preparation known by the name lokron.

According to the invention also the heating wires, the temperature regulator and so.forth,are 5 covered by the impregnated fabric in such a manner that flames produced by short circuit and the like, even after a long time, are not able tosetflretotheouter coverings.

The invention is illustrated by way of example 10 in the accompanying drawing in which Fig. 1 shows an electrically heated cushion according to the invention partly opened.

Fig. 2 shows a detail of the heated cushion in another constructional form,

Fig. 3 shows a further constructional form the cushion according to the invention and Fig. 4 shows a detail of the cushion.

Inthedrawing l aretheheaterwiresof the cushionwhichasusualconsistofanm corem which the heating wire is woimd helically. For the purpose of insulation the heating wireiscoveredintheknownmannerwithasbestos.theheatingwires i arearrangedonorin '-1"' fabric 2 which itself is enclosed by a-ilannel bag I which in general is further protected by a linen has l.

tothe invention the fabric 2 coveringtheheatingwireiisflreproofwithasuitable means and preferably impregnated with a liquid which consists tially of a solution of ammonium sulphate, ammonium chloride, boric acid and borax. A particularly favourable result is obtained with a liquid of 5-10 parts by weight oi ammonium sulphate, 1-4 parts ammonium chloride, 2-5 partsboric acid and 1-3partsof boraxdissolvedinwaterintheproportion of 1-2 to 1-4. The concentration of the salt solution depends on the thickness and kind of fabric. It isadvisabletoaddto thissaltsolution small quantities of condensation product of urea and formaldehyde, known in commerce as lukron, for example, in the proportion of 1-30 and 1-25. With this in liquid according to the invention, the fabric becomes lireproofsothatevenwithanopenflamethefabrlc will notsmouiderorchar. Evenwhentheheatingwiresaregreatlyoverloadednovapoursare producedwhichareunhealthyorimplealantto the user of the cushion.

The impregnation with the said liquid has not only the advantage that cheap fabric, for exampleakindofdish-clotmcan'beusedforthe partiactingasheaterwirecarrierbutalsothe advantage that thissait solutionis very cheap. ll

The action of this salt solution is further increased according to the invention by roughening the fabric as then it soaks up the solution very well.

'In order to avoid any danger of fire accordin to the invention the following construction of the heating cushion is used.

The innermost fabric 2 acting as heating wire carrier consists of one piece and forms two folded parts 5 and B laid one above the other. The asbestos covered heating wires I are placed on the one part 5 and are held by a thin impregnated muslin fabric B'which is fastened to the part 5 of the fabric by quilting indicated at 1. Further, according to the invention, tongues 8 and 9 secured to the part 5 by means of quilted screens and also made of impregnated fabric are provided which serve for covering the temperature I ture of the cable or heater wires, short circuits and ignition thereby may, occur, this covering of the danger points is ineffective protection against fire. Preferably, the tongues according to Figs-2 I are so constructed that they cover the parts to be protected on both sides, that is, according to Fig. 2 the connecting points II are covered by the 'parts l3 and II of the tongue 9.

A further constructional form of the heated cushion according to the invention is illustrated according to Fig. 3. Here a bag i5, which is noninflammable on account of impregnation, is placed over a heater wire carrier l6. In this case the part I6 may consist of combustible material be- .cause the bag l5 completely enclosed any parts that may catch fire. This result is obtained in Asat a similar way that the fabric 2 of Fig. 1 by the parts 5 and 6 being stitched together round the edgm have the insertion of the heating wires.

According to the invention also the connecting points in the heated cushion, for example H, are covered with fireproof pieces or tubes of fabric. At branch points, as, for example, at II, the pieces of fabric are made hose-like and consist according to Fig. 4 of two small tubes l8 drawn over the heating wire I. Over the adjoining ends of which or the connecting point I! a further fireproof fabric tube 20 is drawn.

'.'Ihe above described impregnation according to the invention is not illustrated to heated cushions but can of course be used with the same result in heated covers, mats, aviators clothing, firemens clothing and so forth.

What we claim is: 1. An electrically heated cushion including a heating wire carrier of combustible fabric impregnated with a solution containing ammonium sulphate, ammonium chloride, boric acid and borax and a plurality of protecting covers.

2. An electrically heated-cushion including a heater wire carrier of combustible fabric impregnated with a liquid containing 5-10 parts by weight ammonium sulphate 1-4 parts ammonium chloride, 2-5 parts boric acid, 1-3 parts borax dissolved in water in the proportion of 1-2 to 1-4 and a plurality of protecting covers.

3. An electrically heated cushion including a heating wire carrier of combustible fabric impregnated with a salt solution containing ammonium sulphate, ammonium chloride, boric acid and borax with a small addition of condensation product of urea and formaldehyde.

HANNS mnnnmmz.

GRETE KINDERMANN, at: HUESMANN. 

